Every driver knows the side blind spot. When changing lane the driver must turn head to view the side blind spot to know if vehicles are existed. If the driver forgets to do it, car crash accident may be happen. Returning head to view the side blind spot is very important but brings tire to the driver. Many inventions want to solve this problem, but these inventions are complex, and expensive. Some of them are simple and used with an exterior side mirror, but the image of the blind spot is small, driver cannot see it clearly.